The present invention relates, generally, to the machining art and relates, more particularly, to toolholders, boring bars 1 and the like for holding a cutting insert during a machining operation.
The type of toolholder with which this invention is concerned is characterized by a pocket designed to nestingly accept a cutting insert of a predetermined size and shape and an internally threaded bore spaced from the pocket for retaining an insert clamping assembly. Commonly, the insert clamping assembly includes an elongated finger or top clamp of a preselected length for engaging the cutting insert and a double-ended screw for holding the finger clamp in engagement with the cutting insert. When the cutting insert is nestingly accepted within the toolholder pocket and the preselected finger clamp is held in engagement with the cutting insert, the insert is retained between the bottom, or base, of the pocket and the finger clamp.
A toolholder of the aforedescribed type is limited in that it can only be used to accept and, with a preselected clamping assembly, hold a cutting insert of a predetermined size and shape. Such a limitation requires that if a cutting insert of a predetermined size and shape is required for a machining operation, a toolholder capable of accepting the cutting insert is also required. Therefore, the use of several cutting inserts having various shapes or sizes also requires the availability of several toolholders.
A further limitation of such a toolholder relates to its use in a numerically-controlled or computer numerically-controlled machine tool having a numerical controller which controls the relative movement between the workpiece to be machined and the cutting edge of the cutting insert in response to programmed input. It will be understood, however, that the numerical controller controls such relative movement based upon the position at which the controller believes the cutting edge of the insert is located. Thus, if a machining operation is initiated and the cutting edge of the cutting insert is not positioned where the numerical controller believes it to be, the operation will continue in error. In some machining applications, therefore, if a cutting insert mounted in a machine tool is replaced with another cutting insert, it is important that the cutting edge of the replacement insert be positioned at the location at which the cutting edge of the replaced cutting insert was positioned. If a cutting insert in a machine tool is replaced with a smaller cutting insert (i.e. one have a smaller inscribed circle), the current process involved in aligning the cutting edge of replacement cutting insert with the former position of the cutting edge of the replaced cutting insert is time-consuming and can directly affect the cost of a machined product.
It is, accordingly, an object of the present invention to provide a pocket adaptor for a toolholder as aforedescribed which enables the toolholder to accept, in addition to a first cutting insert which the pocket is designed to accept, a second cutting insert.
Another object of this invention is to provide such an adaptor for a toolholder wherein the second cutting insert is smaller than the first cutting insert and the adaptor positions the cutting edge of the second cutting insert at the location at which the cutting edge of the first cutting insert would be located if the first cutting insert were accepted within the toolholder pocket.
Yet another object of the present invention is to provide such an adaptor for a toolholder and an associated clamping assembly for tightly holding the second cutting insert within the toolholder pocket during a machining operation, such as backfacing or profiling, during which machining pressure tends to pull the insert out of the pocket.